1. Field of the Invention
The present invention relates to a biosensor and a sensing cell array, and more specifically, to a technology to analyze ingredients of adjacent materials depending on electrical characteristics by using a dielectric constant sensor and magnetization characteristics of a magnetization pair detection sensor.
2. Description of the Prior Art
Most semiconductor memory manufacturers have recently developed MTJ (Magnetic Tunnel Junction) and GMR (Giant Magneto Resistive) devices using ferromagnetic materials.
The MTJ device, that comprises two magnetic layers separated by an insulating layer, utilizes spin magnetic permeation phenomenon. In the MTJ device, current better permeates the insulating layer when spin directions are parallel than when anti-parallel in the two magnetic layers. The GMR device, that comprises two magnetic layers separated by a non-magnetic layer, utilizes a giant magnetoresistive phenomenon. In the GMR device, resistance is more differentiated when spin directions are anti-parallel than when parallel in the two magnetic layers.
FIGS. 1a and 1b are diagrams illustrating the operation principle of a conventional MTJ device.
The conventional MTJ device comprises a free ferromagnetic layer 1, a tunnel junction layer 2 and a fixed ferromagnetic layer 3.
When magnetic field lines in the fixed ferromagnetic layer 3 are transmitted into the free ferromagnetic layer 1 through adjacent materials, magnetoresistance varies according to magnetic susceptibilities of the adjacent materials. The magnetic flux density is represented by B=μH (here, μ=magnetic susceptibility, H=magnetic flux). The value of magnetic flux density B varies according to the magnetic susceptibility μ.
As shown in FIG. 1a, if materials having high magnetic susceptibility μ exist between the fixed ferromagnetic layer 3 and the free ferromagnetic layer 1, the magnetic flux density B of the free ferromagnetic layer 1 increases. On the other hand, as shown in FIG. 1b, if materials having low magnetic susceptibility μ exist between the fixed ferromagnetic layer 3 and the free ferromagnetic layer 1, the magnetic flux density B of the free ferromagnetic layer 1 decreases. As a result, the value of magnetoresistance depends on the magnetic susceptibility μ of the adjacent materials between the fixed ferromagnetic layer 3 and the free ferromagnetic layer 1.
FIG. 2 is an analysis table illustrating magnetic susceptibility depending on ingredients of materials adjacent to a MTJ device.
The magnetization constant μ varies depending on kinds and size of ingredients of the adjacent materials.
FIG. 3 is a diagram illustrating capacitance of a general capacitor.
The capacitor comprises a first electrode 4 and a second electrode S. The capacitor has a different dielectric constant ε depending on the distance d between the first electrode 4 and the second electrode 5 and on the area S of the capacitor. That is, the capacitance is C=εS/d (here, S=the area of the capacitor, and d=the distance between the two electrodes). The capacitance C is proportional to the dielectric constant E and the area S of the capacitor, and inversely proportional to the distance d.
FIG. 4 is a diagram illustrating a voltage transmission characteristic of the general capacitor.
Two capacitors connected between a driving plate line PL and a ground voltage terminal have capacitances C1 and C2. A node voltage between the two capacitors is Vs. A driving voltage supplied to the plateline PL by the two capacitors is a driving plate voltage V_PL. Here, the node voltage Vs={C1/(C1+C2)}xV_PL. The node voltage Vs is proportional to the capacitance C1, and is, inverse proportional to the capacitance C2.
FIG. 5 shows that dielectric constant ε is differentiated depending on the kinds and sizes of adjacent materials.
Due to improvement of living environments, people have become more interested in health and life prolongation. After diseases threatening human life occur, people have emphasized preventing the expected diseases rather than simply curing them. Also, they have struggled to control environmental pollution.
As a result, systems to detect various disease causing factors, pollution and toxic substance have been required. To meet this trend, analysis methods of adjacent materials place more weight on biosensors with other physical and chemical sensors.
In order to examine for human diseases using these adjacent material detecting systems, sensing methods are needed for analyzing ingredients of blood, for analyzing ingredients of compounds or for recognizing the skin. However, conventional sensing methods depend on physical or chemical methods for analyzing material ingredients. As a result, large equipment and cost for are required for such testing. Since it takes a long time for such tests, it is difficult to analyze ingredients of various adjacent materials.